Offshore drilling apparatus and method

ABSTRACT

Method and apparatus for taking core from a submerged earth formation that including drilling a casing into an earth formation a number of feet. A flotation tank is provided on the upper end of the casing while a cushion drum assembly is mounted on the lower end of the casing to control the rate of descent of the rotating casing into the formation; and such an assembly or weight on the lower end of the casing is provided to maintain the major portion of the casing in tension. After the casing is extended into the earth formation, a drill unit is supportedly mounted on the casing, a drill stem extended down through the casing and the drill stem drilled into the formation for continuing the core-taking operation.

United States Patent Primary Examiner-Marvin A. Champion AssistantExaminer-Richard E. Favreau Attorney-Bugger, Peterson, Johnson & WestmanABSTRACT: Method and apparatus for taking core from a submerged earthfonnation that including drilling a casing into an earth fonnation anumber of feet. A flotation tank is provided on the upper end of thecasing while a cushion drum am sembly is mounted on the lower end of thecasing to control the rate of descent of the rotating casing into theformation; and such an assembly or weight on the lower end of the casingis provided to maintain the major portion of the casing in tension.After the casing is extended into the earth formation, a drill unit issupportedly mounted on the casing, a drill stem extended down throughthe casing and the drill stem drilled into the formation for continuingthe core-taking operation.

4? HI T /5'c PATENIED JMI 4:972 3,631. 932

SHEET 3 [IF 4 FIG! 4 OFFSHORE DRILLING APPARATUS AND METHOD BACKGROUNDOF THE INVENTION The invention relates to offshore drilling operations,particularly to core drilling and the taking of samples of an earthformation.

Travers et al. U.S. Pat. No. 3,196,958, discloses using negativebuoyance in a float that is attached to the upper end of a drill pipewhile drilling a hole in an underwater earth formation; and after thehole is drilled, a casing extended into the hole and a foundationprovided at the bottom to cement the casing in place, the float isevacuated to place the casing under tension. However, in using prior artapparatus there is the problem of retaining the casing substantiallyvertical while it is being lowered prior to any underwater drilling; andafter the casing is lowered, to control the initial rate of penetrationof the underwater earth formation, especially where the bottom is mucky.Also, in core-drilling operations, many times the recovery of the firstfew inches or feet of core of an underwater earth formation areconsidered to be of prime importance. One example is for ascertaining ifvaluable minerals have been deposited on the ocean floor. However, withprior an apparatus and methods, frequently the first few inches of coreare lost, or only partially recovered, or are not recovered in a mannerthat accurately reflects the layers of the earth formation. This isespecially true where the bottom is soft or mucky. In order to overcomeproblems of the above-mentioned nature, this invention has been made.

SUMMARY OF THE INVENTION Underwater drilling apparatus and method ofusing, including a casing having float means attached to the upper endportion and a weight mounted adjacent but spaced from the casing lowerterminal end that-is used during the initial coring operation andthereafter has a drill stem extended therethrough for further coredrilling. In mucky bottoms, a cushion drum assembly that includes saidweight is provided to control the rate of descent of the casing.

One of the objects of the invention is to provide new and novel casingstructure that is maintained in tension for taking an initial footage ofcore from an underwater earth formation and thereafter serve as thestructure for supporting a drill unit for further coring. Another objectof this invention is to provide new and novel apparatus for controllingthe rate of initial penetration of an underwater earth fonnation duringa drilling operation. A

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective viewillustrating a vessel, and a casing having a flotation tank and drumcushion assembly thereon after the casing has been lowered so that saidassembly rests on a submerged earth formation, portions of casing beingbroken away;

FIG. 2 is a vertical cross-sectional view of the lower end portion ofthe structure illustrated in FIG. 1 prior to the initiation of thecore-taking step, a vertically inten'nediate part being broken away;

FIG. 3 is a crosssectional view generally taken along the line and inthe direction of the arrows 33 of FIG. 2;

FIG. 4 is a vertical cross-sectional view of the lower end of the casingand a retractable wire line core or sample barrel latched therein;

FIG. 5' is a perspective view, part in cross section, to show theflotation tank mounted on the casing;

FIG. 6 is a perspective view showing the drill unit platform mounted onthe casing and the drill unit mounted on the platform for operating thedrill stem extending through the casing;

FIG. 7 is a view similar to that of FIG. 2 other than the weights in thedrum and casing have been operated to the lowermost position of saidweights relative the drum; and

FIG. 8 is a horizontal cross-sectional view of the lower end portion ofthe casing of FIG. 6 to indicate that a core barrel inner tube assemblyis located within the drill stem.

Referring now to the drawings, in FIG. 1 there is illustrated a drillingvessel, barge or platform 10 of a suitable floating type that isfloating on the surface of a body of water 11. The vessel issubstantially fixed over a preselected floating location by suitablevessel-positioning means (not shown) or by being anchored to the oceanfloor 12. The vessel includes a derrick and drill unit 13 for initiallylowering the sections of the casing 15 and cushion drum, generallydesignated 16, supporting the various sections of the casing as thecasing is being assembled, and initially rotating the casing to drillthe lower end of the casing into the ocean floor as will become moreapparent hereinafter.

The casing, when in an assembled condition, has an enlarged diameterlower end portion 15:; that may extend, for example, 200 feet. The lowerend of the casing portion is provided with a diamond drill bit 150 thatis mounted thereon to rotate therewith. Advantageously, the upper endportion of the casing 15b may be of a smaller outside diameter thanportion 150, portion 15b extending above. the level of the water ll.Mounted on the casing portion 15a in a selected axial position, forexample 22 feet above the lower edge of the drill bit 15c is a bearingsupport member 18 (see FIG. 2). An annular weight 19 has a casingportion rotatably extended therethrough and is mounted on the bearingmember 18. The upper end portion of weight 19 is of reduced diameter toprovide a shoulder 19a to support the flange portion 210 of the drum 21of the cushion drum assembly 16. The enlarged diametric portion of theweight 19 is located within the annular main body 21b of the drum 21 andforms a sliding fit with the inner peripheral wall thereof. A seal 22 isprovided in a groove on the lower end portion of the weight to provide asealing fit with the inner peripheral wall of the drum. The drum wall21b is provided with one or more vent apertures 23 at an elevation thatis slightly below the lower surface of the weight 19.

Secured to the lower edge of the drum wall 2lbis an annular shield 25,theshield having a central aperture 26 that is defined by the lower edge25a of the shield. The shield has an outer terminal edge 25b, the radiusof curvature of edge 25b being substantially greater than that of thedrum wall 21b while the radius of curvature of aperture 26 beingsubstantially less than that of the inner peripheral radius of the drumwall. When the drum is in a vertical upright condition such asillustrated in FIG. 2, the shield in vertical cross section curvesrelatively sharply upwardly and slightly outwardly, thence curvespredominantly outwardly and slightly upwardly; and adjacent to terminaledge 25b, curves slightly downwardly and outwardly. As a result, theedge 25b is located at a lower elevation than the edge 25a while thedrum wall 21!: is secured to the shield at a higher elevau'on than edge25b. A plurality of reinforcing web plates 27 are welded to the shieldsurface opposite the drum wall 21b, the web plates extending fromadjacent the aperture 26 to adjacent the terminal edge 25b.Advantageously, one or more weights 28 are located in surroundingrelationship to the drum wall 21b and supported by the shield. Also oneor more weights 24 are in surrounding relationship to the casing and arevertically stacked on the weight 19; the outer diameter of theadditional weights 24 being less than the inner diameter of the flange21a of the drum. The casing is rotatably relative to weights 24.

Mounted within the interior of the drum at a slightly higher elevationthan the shield is an annular support member 30, said support member inturn mounting an annular member 3I that mounts a seal member 32 toretain the casing in concentric relationship relative the drum wall andat the same time permit the casing to freely rotate and move verticallyrelative the drum wall 21b. Additionally members 30-32 prevent waterthereabove that is in the drum from exhausting through aperture 26. Theinterior of the drum vertically between the support member 30 and thelower surface of the weight 19 in its elevated condition relative thedrum wali such as illustrated in FIG. 2 is free of structure other thanfor the portion of the casing that extends vertically therebetween At anelevation just above the support member 30 or to open through thesupport member, a relief valve 33 is mounted on the drum wall exteriorof the casing to open into the interior of the drum. The relief valvehas an outlet that opens to the flow control valve 34 to control therate of exhaust of water from the drum as will be more fully set forthhereinafter.

The upper part of the casing portion 15b extends through acompartmentalized annular tank 40 (see FIG. Hearing support members 41retain the tank in a fixed position relative the casing but at the sametime permit the casing to rotate relative the tank. The tank is locatedat a substantial elevation beneath the surface of the water, for example20-40 feet. A plurality of lines 49 open into the tank, one set of saidlines extending back to the vessel for permitting the pumping ofcompressed air into the various compartments tank while the other set oflines is provided with a suitable control valve for controlling theinlet and exhaust of water from the compartments of the tanks. Althoughnot shown, the water lines extend adjacent the bottom ofthe respectivecompartment.

Once the lower end of the casing has been drilled into the earthformation as will be described hereinafter, a platform 42 is mountedonto the upper end of the casing 15, the platform in part beingsupported by an annular member 43 that is secured to the casing adjacentthe upper edge thereof and the remainder by an annular member 44 that issecured to the easing intermediate the level of the water and member 43.A plurality of braces 45 at their one ends are attached to member 44 andthe opposite ends of the platform. Mounted on the platform 42 to besupported thereby is a conventional drilling unit, generally designatedat 46. Appropriate lines (not shown) for conducting fluid to the drillunit and for controlling the drill unit extend to the vessel. Further, acatwalk 47 and guy lines 48 may be extending between the platform andthe vessel although weight of the drill unit and platform 42 are solelysupported by the casing 15.

Using the apparatus of this invention, the vessel is moved to a locationwhere the core is to be taken advantageously underwater televisioncamera being utilized to aid in the selection of an appropriate spot fordrilling. If from the viewing of the television camera it appears thatthe ocean floor is of a mucky consistency, or it is uncertain as towhether or not it is of a mucky consistency, then the lower end of thecasing portion a is extended through the weights and into the drum, anda bit 15c mounted on the lower end of the casing so that the parts arelocated in a relative position such as illustrated in FIG. 2 and thebearing 18 supports the weights and drum assembly when the casingportion is upright. Further, based upon the depth of the ocean floor atthe point of drilling, the desired rate of penetration of the formation12 by the drill bit 150, the weights and the flotation tank being used,the vale 33 is preset to open at a predetennined pressure and the flowcontrol valve 34 is set to limit the rate of exhaust of liquidtherethrough. Now, the lower end of the casing with the cushion drumassembly mounted thereon is lowered into the water. During the loweringprocess, air vents through aper tures 23 and the interior of the drumfills with water. Additional sections of the casing are connected to oneanother until the time that the shield 27 bears against the ocean floor.

A flotation tank 40 is mounted on a section of the casing to be locatedat a selected distance below the level of the body of water, for example-40 feet and air is pumped in or water is allowed to enter the tank toexert the desired degree of upward force on the casing such that theneutral point between the load condition of the casing and the tensionforce that is exerted by tank 40 is located, for example, within rangeof approximately 50 to 150 feet above the surface of the ocean floor,i.e. within the length of section 15a.

Assuming that the ocean floor is a mucky bottom, the edge, a penetratesthe ocean floor and the shield continues to sink until part orsubstantially all of the surface thereof abuts against the bottom. To benoted is that during the initial period of sinking, the part of thebottom circumscribed by edge 25a protrudes through the aperture 26upwardly to be at a location beneath the core bit 150. However, to benoted is that the apparatus functions properly even only if a part ofthe shield abuts against the bottom, for example, a sloping bottom.

Either prior to, or after the casing has been lowered so that thecushion drum assembly bears against the submerged earth formation, aretractable wire line core barrel inner'tube assembly or wire linesampling barrel assembly, generally designated 60, is lowered in thecasing until the latches 61 seat in the latch seat a in the lower part(core barrel outer tube) 70 of the casing, the suspension ring 62 seatson the landing ring 70b mounted in the casing, and the inner tube 68extends to a lower elevation than the casing bit. A bearing housingassembly 63 connects the inner tube to the spindle 64 which in turn isconnected to the latch body 65. A spring 66 on the spindle resilientlyurges the bearing housing to move the inner tube away from the latchbody, but permits the inner tube retracting into the casing in the eventthe inner tube engages a relatively hard earth formation. The corebarrel outer tube 70 includes the drill bit 15c.

Preferably, the inner tube extends a few inches downwardly below bit15c, and at a time prior to lowering the casing relative the drum toinitially penetrate the earth formation with the bit 15c, the lowerterminal edge of the inner tube 68 is located at a higher elevation thanaperture 26. As a result, the drilling fluid flowing between the casingand the inner tube can flow radially outwardly across the drill bit factwhereby such fluid flow does not tend to wash away any of the softbottom directly beneath the inner tube.

Now upon proper adjustment of the downward force exerted on the casing(controlling the degree of buoyancy exerted by tank 40 by, for example,exhausting water from the tank 40) the gravitational force exerted bythe casing and the weights 19, 24, 28 in a downward direction againstthe water within the drum increases to a pressure to open valve 33 andwater starts to flow out of the drum through valves 33 and 34. Valve 33had been previously preset to open at a higher pressure than thepressure of the water at the elevation of the surface of formation 12.At the same time a drill unit which is supported from the vessel andwhich has been connected to the upper end of the casing is operated torotate the casing. As the casing rotates and the casing-weightcombination moves downwardly within the drum wall the core-taking cycleis begun. The drilling fluid passing through the casing can come upalong the outside of the casing, flow through aperture 26 and thencethrough channel 83 that opens through member 30 and the adjacent part ofthe drum to permit water below members 30-32 to exhaust to outside ofthe drum.

After the casing is moved downwardly a sufficient distance that theweight 19 rests against the support member 30, the drill unit presentlymounted on the upper end of the casing is stopped and the core barrelinner tube assembly 60 is retracted with conventional wire line overshotequipment. At this time, the casing extends a sufficient distance intothe earth formation to anchor" the lower end of the casing.

After the core barrel inner tube assembly 60 has been retracted, and thedrill unit connected to the casing disattached, the platform, includingmembers 43-45, and the drill unit 46 are mounted on the upper end of thecasing such as illustrated in FIG. 6. Now a drill stem 59 having a corebarrel outer tube 59a on the lower end thereof is lowered through thecasing to extend from the drill unit 46 to bit 15c. A conventional wireline inner tube assembly 5% is lowered in the drill stem 59 until itlatches in place in the core barrel outer tube 59a and thence the coringoperation is continued. The assembly 59b may be of the same constructionas that of assembly 60, except of a smaller diameter and therefore isnot fully illustrated. It is to be noted that at this time the physicalweight of the drill unit 46 is supported by the casing and thereforemovement of the vessel 10 does not affect the drilling operation. Nowthe drill stem is rotated to drill further into the earth formation andcore recovered through the use of assembly 59b.

The tanks and weights retain the casing in tension to prevent bucklingand also retain the casing in a vertical direction when the casing isbeing lowered..The weight of the weights in part depends upon the typeof bottom (mucky or rocky bottom) and the depth between the surface andthe bottom. If the depth is, for example, 600 feet of water, thenusually the weights would total 2,000-4,000 pounds. Under suchconditions, the flotation tanks would advantageously be of a size toprovide 2,000 pounds flotation.

As a further example of the invention but not as a limitation thereof,if the drilling is to be carried out in a mucky bottom, then thediameter of the drum wall is advantageously 6 feet while the outerdiameter of the lower portion a of the casing is 5%; inches; while ifthe drilling is to be carried out on a firmer bottom, then using thesame diameter casing, the drum wall may be of a diameter of 18 inches.

If it is known the bottom is a solid type, for example, of rockformation, then the drum and shield need not be used, but rather thecasing drilled into the rock formation until the weight 19 bears againstthe rock formation. Then the drill unit 46 is mounted on the casing anddrill stem 59 extended into the casing.

What is claimed is:

1. In apparatus for drilling into an underwater earth formation, anelongated casing having an upper end portion, a lower end portion and aterminal lower end, weight means mounted on the lower end portion of thecasing a preselected distance from said terminal lower end, said weightmeans including a weight member in relative rotatable surroundingrelationship to the casing and bearing means mounted on the casing formounting the weight means on the casing and permitting rotation of thecasing relative the weight member, float means mounted on the casingupper end portion a substantial distance beneath the surface of thewater for supporting at least part of the weight of the casing andcooperating with the weight means to retain a major portion of thelength of the casing in tension, a platform mounted on said casing at anelevation above the float means and supported by the casing, and a drillunit mounted on said platform.

2. In apparatus for drilling into an underwater earth formation, anelongated casing having an upper end portion, a lower end portion and aterminal lower end, weight means mounted on the lower end portion of thecasing a preselected distance from said terminal lower end, said weightmeans including a weight member in relative rotatable surroundingrelationship to the casing and bearing means mounted on the casing formounting the weight means on the casing and permitting rotation of thecasing relative the weight member, float means mounted on the casingupper end portion for supporting at least part of the weight of thecasing and cooperating with the weight means to retain a major portionof the length of the casing in tension, said casing lower end portionincluding a core barrel outer tube having a latch seat, and aretractable wire line core barrel inner tube mounted in said core barrelouter tube.

3. The apparatus of claim 2, further characterized in that said corebarrel outer tube includes a drill bit.

4. The apparatus of claim 2, further characterized in that there isprovided a drum having an upper end portion and a lower end portion,said drum upper and lower end portions respectively having a top openingand a bottom opening that are of larger diameters than the casing, saiddrum upper end portion and weight means having cooperating means forsuspendingly supporting the drum from the weight means to extend to asubstantially lower elevation than the weight means while permitting theweight means to move downwardly in the drum, said weight means havingmeans for forming a sliding fluid seal with the drum.

5. The apparatus of claim 4 further characterized in that valve means isattached to the lower end portion of the drum to open to the interiorthereof for providing a liquid discharge passageway to permit the escapeof liquid from the interior of the drum only after the liquid pressurein the drum exceeds a preselected level.

6. The apparatus of claim 5 further characterized in that a flow controlvalve is connected to the valve means to control the rate of dischargeof liquid through the valve means and that the drum includes means forventing air prior to any substantial downward movement of the weightmeans in the drum.

7. The apparatus of claim 6 further characterized in that said ventmeans comprises a drum wall portion having a vent aperture that is at aslightly lower elevation than the seal means when the drum issuspendingly supported from the weight means.

8. The apparatus of claim 6 further characterized in that there isprovided a shield that is attached to the drum lower end portion, saidshield having an opening of a size for the casing to pass therethrough.

9. The apparatus of claim 8 further characterized in that said shieldhas an outer peripheral edge bounding a substantially larger area thanthe cross-sectional area of the drum transverse to the direction ofelongation of the casing, and that the shield is of a shape to slopedownwardly and inwardly from its outer peripheral edge in a directiontoward said shield opening.

10. The apparatus of claim 8 further characterized in that a platform ismounted on said casing at an elevation above the float means and issupported by the casing and that a drill unit is mounted on theplatform.

11. The apparatus of claim 8 further characterized in that there isprovided means in the drum for forming a rotary fluid seal between thedrum and the casing at an elevation between the shield and the openingof the valve means to the drum.

12. Apparatus for taking core samples from an underwater earthformation, comprising an elongated casing having an upper end portionand a lower end portion, said lower end portion including a drill bit,at least one weight, bearing means mounted on the lower end portion apreselected distance from the drill bit for mountingly retaining saidweight on the casing substantially spaced from the drill bit, anelongated drum of a greater length than said preselected distanceextending in surrounding relationship to said weight, said drum andweight having cooperating means for suspendingly supporting the drumfrom the weight while permitting the weight to move downwardly in thedrum, means on the weight for forming a slidable fluid seal with thedrum, and means opening to the interior of the drum for controlling therate of exhaust of water from the drum as the weight moves downwardly inthe drum.

13. The apparatus of claim 12 further characterized in that thelast-mentioned means includes a valve set to open at a predeterminedpressure of liquid in the drum, and that an annular shield is mounted onthe lower end of the drum for engaging an earth formation, said shieldhaving a central aperture for the casing to pass through, said aperturebeing at a lower elevation than the drill bit when the weightsuspendingly supports the drum.

14. Apparatus for drilling into an underwater earth formation comprisinga casing having an upper end portion, a lower end portion and a drillbit lower terminal end portion, float means attached to the casing upperend portion a substantial distance beneath the surface of the water forsupporting a substantial part of the weight of the casing, means forrotating the casing and first means attached to the lower end portion ofthe casing for engaging the underwater earth formation and controllingthe rate of descent of the casing as it is being rotated.

15. The apparatus of claim 14 further characterized in that said firstmeans comprises an elongated drum having an upper end portion and alower end portion, second means opening into the interior of the lowerend portion of the drum for discharging liquid from the drum at acontrolled rate, and a weight attached to the casing a preselecteddistance above the drill bit to move with the casing and being movabledownwardly in the drum from a first position to a lower second positionto force water out of the drum through the second means.

16. The apparatus of claim further characterized in that said weight hasmeans to form a slidable fluid seal with the drum, that said drum hasvent means for exhausting air from the drum, said vent means being at ahigher elevation than the above-mentioned sealing means between the drumand the weight after the weight has moved a short distance downwardlyfrom its first position toward its second position, that the secondmeans includes valve means opening into the drum that opens at a higherpressure than the pressure of the liquid in the drum when the drum isclosely adjacent the earth formation, and that the first means includesmeans at a lower elevation than the opening of the valve means to thedrum for forming a fluid seal between the drum and the casing whilepermitting the casing to move relative the drum.

17. A method of drilling an earth fonnation underwater wherein anelongated casing having an upper end portion, a lower end portion and alower terminal end is used, said method comprising the steps ofattachably mounting a weight member on the lower end of the casing apreselected distance from the lower terminal end of the casing, loweringthe casing in water until the lower end of the casing is adjacent theearth fonnation, attaching a flotation tank to the casing upper endportion to retain at least a major portion of the casing in tension,further lowering the casing until the lower end of the easing abutsagainst the earth formation, drilling the casing to a depth in the earthformation that the weight member is located substantially more closelyadjacent the earth formation than when the casing lower end abuttedagainst said formation, then mounting a drill unit platform on thecasing for being supported thereby and then utilizing the drill unit tolower a drill stem through the casing and operate the drill stem topenetrate the earth formation to a greater depth than the casrng.

18. The method of claim 17 further characterized in that the drillingwith a casing is continued until the weight member abuts against theearth formation.

19. The method of claim 18 further characterized in that the step ofattaching a weight member also includes mounting a drum to at least inpart surround said weight member and form a cylinder to effectivelyprovide a piston cylinder combination and presetting a flow controlvalve to open to permit water to exhaust out of said combination at acontrolled rate of flow after the water pressure in the casing hasexceeded a preselected level to control the rate of penetration of thecasing into the earth formation.

20. In a method of'drilling into an earth formation below the surface ofa body of water wherein an elongated casing having a lower end and anupper end portion is used, the steps of attaching a cushion drumassembly to surround a substantial length of the lower end portion ofthe casing including mounting a weight on the casing a preselecteddistance above the lower end of the casing and suspendingly supporting adrum on the weight, setting a valve to exhaust water from the interiorof the drum at a pressure higher than the pressure of water in theinterior of the drum at the time the drum has been lowered to the earthformation, lowering the casing, applying a buoyant force to the upperend portion of the casing through a submerged float to retain a majorportion of the length of the casing between the float and the weight intension, and imparting a rotary motion to the casing when the drumdevice has engaged the earth formation.

21. The method of claim 20 further characterized in that the rate ofexhaust of the water from the drum is controlled to thereby control therate of descent of the casing as it drills into the earth formation.

22. The method of claim 21 further characterized in mounting a drillunit on the upper end of the casing to be supported thereby after thecasing has been drilled a selected depth into the earth formation, andoperating a drill stem through said casing to drill a deeper hole in theearth formation, and collecting core samples through the use of thedrill stem.

23. The apparatus of claim 22 further characterized in that there isprovided a drill steam extendedthrough the casing and operated by thedrill unit for penetrating the earth formation to a greater depth thanthe casing.

24. Apparatus for drilling into an underwater earth formation comprisinga casing having an upper end portion, a lower end portion and a drillbit lower terminal end portion, float means attached to the casing upperend portion for supporting a substantial part of the weight of thecasing, means for rotating the casing and first means attached to thelower end portion of the casing for engaging the underwater earthformation, said first means including weight means mounted on the lowerend portion of the casing a preselected distance from said lowerterminal end portion to cooperate with the float means to retain a majorportion of the length of the casing in tension, and a drum having anupper end portion and a lower end portion engageable with the underwaterearth formation, said drum upper and lower end portions respectivelyhaving a top opening and a bottom opening that are of larger diametersthan the casing, said drum upper end portion and weight means havingcooperating means for suspendingly supporting the drum from the weightmeans to extend to a substantially lower elevation than the weight meanswhile permitting the weight means to move downwardly in the drum, saidweight means having means for forming a close sliding fit with the drum.

25. Apparatus for drilling into an underwater earth formation comprisinga casing having an upper end portion, a lower end portion and anearth-penetrating lower terminal end portion, first means attached tothe casing upper end portion for supporting a substantial part of theweight of the casing, second means attached to the casing for moving thecasing to penetrate the underwater earth formation and third meansattached to the lower end portion of the casing for engaging theunderwater earth formation to control the rate of penetration of theunderwater earth formation by the casing as the casing is moved by thesecond means.

26. The apparatus of claim 25 further characterized in that the firstmeans comprises float means attached to the casing, and that the secondmeans is attached to the casing above the float means.

i i I t

1. In apparatus for drilling into an underwater earth formation, anelongated casing having an upper end portion, a lower end portion and aterminal lower end, weight means mounted on the lower end portion of thecasing a preselected distance from said terminal lower end, said weightmeans including a weight member in relative rotatable surroundingrelationship to the casing and bearing means mounted on the casing formounting the weight means on the casing and permitting rotation of thecasing relative the weight member, float means mounted on the casingupper end portion a substantial distance beneath the surface of thewater for supporting at least part of the weight of the casing andcooperating with the weight means to retain a major portion of thelength of the casing in tension, a platform mounted on said casing at anelevation above the float means and supported by the casing, and a drillunit mounted on said platform.
 2. In apparatus for drilling into anunderwater earth formation, an elongated casing having an upper endportion, a lower end portion and a terminal lower end, weight meansmounted on the lower end portion of the casing a preselected distancefrom said terminal lower end, said weight means including a weightmember in relative rotatable surrounding relationship to the casing andbearing means mounted on the casing for mounting the weight means on thecasing and permitting rotation of the casing relative the weight member,float means mounted on the casing upper end portion for supporting atleast part of the weight of the casing and cooperating with the weightmeans to retain a major portion of the length of the casing in tension,said casing lower end portion including a core barrel outer tube havinga latch seat, and a retractable wire line core barrel inner tube mountedin said core barrel outer tube.
 3. The apparatus of claim 2, furthercharacterized in that said core barrel outer tube includes a drill bit.4. The apparatus of claim 2, further characterized in that there isprovided a drum having an upper end portion and a lower end portion,said drum upper and lower end portions respectively having a top openingand a bottom opening that are of larger diameters than the casing, saiddrum upper end portion and weight means having cooperating means forsuspendingly supporting the drum from the weight means to extend to asubstantially lower elevation than the weight means while permitting theweight means to move downwardly in the drum, said weight means havingmeans for forming a sliding fluid seal with the drum.
 5. The apparatusof claim 4 further characterized in that valve means is attached to thelower end portion of the drum to open to the interior thereof forproviding a liquid discharge passageway to permit the escape of liquidfrom the interior of the drum only after the liquid pressure in the drumexceeds a preselected level.
 6. The apparatus of claim 5 furthercharacterized in that a flow control valve is connected to the valvemeans to control the rate of discharge of liquid through the valve meansand that the drum includes means for venting air prior to anysubstantial downward movement of the weight means in the drum.
 7. Theapparatus of claim 6 further characterized in that said vent meanscomprises a drum wall portion having a vent aperture that is at aslightly lower elevation than the seal means when the drum issuspendingly supported from the weight means.
 8. The apparatus of claim6 further characterized in that there is provided a shield that isattached to the drum lower end portion, said shield having an opening ofa size for the casing to pass therethrough.
 9. The apparatus of claim 8further characterized in that said shield has an outer peripheral edgebounding a substantially larger area than the cross-sectional area ofthe drum transverse to the direction of elongation of the casing, andthat the shield is of a shape to slope downwardly and inwardly from itsouter peripheral edge in a direction toward said shield opening.
 10. Theapparatus of claim 8 further characterized in that a platform is mountedon said casing at an elevation above the float means and is supported bythe casing and that a drill unit is mounted on the platform.
 11. Theapparatus of claim 8 further characterized in that there is providedmeans in the drum for forming a rotary fluid seal between the drum andthe casing at an elevation between the shield and the opening of thevalve means to the drum.
 12. Apparatus for taking core samples from anunderwater earth formation, comprising an elongated casing having anupper end portion and a lower end portion, said lower end portionincluding a drill bit, at least one weight, bearing means mounted on thelower end portion a preselected distance from the drill bit formountingly retaining said weight on the casing substantially spaced fromthe drill bit, an elongated drum of a greater length than saidpreselected distance extending in surrounding relationship to saidweight, said drum and weight having cooperating means for suspendinglysupporting the drum from the weight while permitting the weight to movedownwardly in the drum, means on the weight for forming a slidable fluidseal with the drum, and means opening to the interior of the drum forcontrolling the rate of exhaust of water from the drum as the weightmoves downwardly in the drum.
 13. The apparatus of claim 12 furthercharacterized in that the last-mentioned means includes a valve set toopen at a predetermined pressure of liquid in the drum, and that anannular shield is mounted on the lower end of the drum for engaging anearth formation, said shield having a central aperture for the casing topass through, said aperture being at a lower elevation than the drillbit when the weight suspendingly supports the drum.
 14. Apparatus fordrilling into an underwater earth formation comprising a casing havingan upper end portion, a lower end portion and a drill bit lower terminalend portion, float means attached to the casing upper end portion asubstantial distance beneath the surface of the water for supporting asubstantial part of the weight of the casing, means for rotating thecasing and first means attached to the lower end portion of the casingfor engaging the underwater earth formation and controlling the rate ofdescent of the casing as it is being rotated.
 15. The apparatus of claim14 further characterized in that said first means comprises an elongateddrum having an upper end portion and a lower end portion, second meansopening into the interior of the lower end portion of the drum fordischarging liquid from the drum at a controlled rate, and a weightattached to the casing a preselected distance above the drill bit tomove with the casing and being movable downwardly in the drum from afirst position to a lower second position to force water out of the drumthrough the second means.
 16. The apparatus of claim 15 furthercharacterized in that said weight has means to form a slidable fluidseal with the drum, that said drum has vent means for exhausting airfrom the drum, said vent means being at a higher elevation than theabove-mentioned sealing means between the drum and the weight after theweight has moved a short distance downwardly from its first positiontoward its second position, that the second means includes valve meansopening into the drum that opens at a higher pressure than the pressureof the liquid in the drum when the drum is closely adjacent the earthformation, and that the first means includes means at a lower elevationthan the opening of the valve means to the drum for forming a fluid sealbetween the drum and the casing while permitting the casing to moverelative the drum.
 17. A method of drilling an earth formationunderwater wherein an elongated casing having an upper end portion, aloWer end portion and a lower terminal end is used, said methodcomprising the steps of attachably mounting a weight member on the lowerend of the casing a preselected distance from the lower terminal end ofthe casing, lowering the casing in water until the lower end of thecasing is adjacent the earth formation, attaching a flotation tank tothe casing upper end portion to retain at least a major portion of thecasing in tension, further lowering the casing until the lower end ofthe casing abuts against the earth formation, drilling the casing to adepth in the earth formation that the weight member is locatedsubstantially more closely adjacent the earth formation than when thecasing lower end abutted against said formation, then mounting a drillunit platform on the casing for being supported thereby and thenutilizing the drill unit to lower a drill stem through the casing andoperate the drill stem to penetrate the earth formation to a greaterdepth than the casing.
 18. The method of claim 17 further characterizedin that the drilling with a casing is continued until the weight memberabuts against the earth formation.
 19. The method of claim 18 furthercharacterized in that the step of attaching a weight member alsoincludes mounting a drum to at least in part surround said weight memberand form a cylinder to effectively provide a piston cylinder combinationand presetting a flow control valve to open to permit water to exhaustout of said combination at a controlled rate of flow after the waterpressure in the casing has exceeded a preselected level to control therate of penetration of the casing into the earth formation.
 20. In amethod of drilling into an earth formation below the surface of a bodyof water wherein an elongated casing having a lower end and an upper endportion is used, the steps of attaching a cushion drum assembly tosurround a substantial length of the lower end portion of the casingincluding mounting a weight on the casing a preselected distance abovethe lower end of the casing and suspendingly supporting a drum on theweight, setting a valve to exhaust water from the interior of the drumat a pressure higher than the pressure of water in the interior of thedrum at the time the drum has been lowered to the earth formation,lowering the casing, applying a buoyant force to the upper end portionof the casing through a submerged float to retain a major portion of thelength of the casing between the float and the weight in tension, andimparting a rotary motion to the casing when the drum device has engagedthe earth formation.
 21. The method of claim 20 further characterized inthat the rate of exhaust of the water from the drum is controlled tothereby control the rate of descent of the casing as it drills into theearth formation.
 22. The method of claim 21 further characterized inmounting a drill unit on the upper end of the casing to be supportedthereby after the casing has been drilled a selected depth into theearth formation, and operating a drill stem through said casing to drilla deeper hole in the earth formation, and collecting core samplesthrough the use of the drill stem.
 23. The apparatus of claim 22 furthercharacterized in that there is provided a drill steam extended throughthe casing and operated by the drill unit for penetrating the earthformation to a greater depth than the casing.
 24. Apparatus for drillinginto an underwater earth formation comprising a casing having an upperend portion, a lower end portion and a drill bit lower terminal endportion, float means attached to the casing upper end portion forsupporting a substantial part of the weight of the casing, means forrotating the casing and first means attached to the lower end portion ofthe casing for engaging the underwater earth formation, said first meansincluding weight means mounted on the lower end portion of the casing apreselected distance from said lower terminal end portion to cooperatewith the float means to retain a major portion of the length of thecasing in tension, and a drum having an upper end portion and a lowerend portion engageable with the underwater earth formation, said drumupper and lower end portions respectively having a top opening and abottom opening that are of larger diameters than the casing, said drumupper end portion and weight means having cooperating means forsuspendingly supporting the drum from the weight means to extend to asubstantially lower elevation than the weight means while permitting theweight means to move downwardly in the drum, said weight means havingmeans for forming a close sliding fit with the drum.
 25. Apparatus fordrilling into an underwater earth formation comprising a casing havingan upper end portion, a lower end portion and an earth-penetrating lowerterminal end portion, first means attached to the casing upper endportion for supporting a substantial part of the weight of the casing,second means attached to the casing for moving the casing to penetratethe underwater earth formation and third means attached to the lower endportion of the casing for engaging the underwater earth formation tocontrol the rate of penetration of the underwater earth formation by thecasing as the casing is moved by the second means.
 26. The apparatus ofclaim 25 further characterized in that the first means comprises floatmeans attached to the casing, and that the second means is attached tothe casing above the float means.